Reinforced concrete stands as the predominant structural material for contemporary infrastructure. In chlorine-corrosive environments, steel bars undergo electrochemical reactions and pitting, leading to cross-sectional loss. Additionally, concrete cracking accelerates the corrosion rate of steel bars. These two factors—concrete cracking, and corrosion pit depth plus steel yielding contribute to the deterioration of the mechanical properties of reinforced concrete structures. For the mechanical modeling of RC frame structures exposed to chloride corrosion environments, three internal variables (damage, plasticity, and corrosion) are incorporated into a constitutive equation to calculate the mechanical response under both mechanical and chemical conditions, accounting for the deterioration of reinforcement materials caused by chloride-induced corrosion. A lumped damage mechanics model serves as the foundational approach to establish the comprehensive mechanical model aimed at assessing the performance of RC frames. The energy dissipation resulting from the three internal variables is lumped within the inelastic zones at the ends of the frame finite element. In conjunction with thermodynamic theory, the lowering of Gibbs energy serves as the driving force representing the dissipation of energy from these coupled internal variables, and the evolution laws of the three internal variables are defined in this paper. This approach is capable to evaluate the mechanical behavior of RC structures, including bridge piers, under corrosive environments throughout their service life.